Does hemiplegic shoulder pain share clinical and sensory characteristics with central neuropathic pain? A comparative study.

Background: Hemiplegic shoulder pain (HSP) is a common poststroke complication and is considered to be a chronic pain syndrome. It is negatively correlated with the functional recovery of the affected arm and the quality of life of the individual. It also leads to a longer length of stay in rehabilitation. Today, there is no consensus as to the underlying mechanism causing HSP, making the syndrome difficult to treat.
Aim: The aim of this study was to compare the clinical and sensory profile of individuals with HSP to that of individuals with established central neuropathic pain (CNP) in order to identify common features and the presence of neuropathic components in HSP.
Design: Cross sectional controlled study.
Settings: Outpatient rehabilitation clinics.
Population: Sixteen chronic HSP patients and 18 chronic CNP patients with spinal cord injury (SCI-CNP).
Methods: The chronic pain characteristics, thresholds of thermal and tactile sensations and presence of pathological sensations were compared between groups, and between painful and pain free body regions within groups. Correlations were calculated between HSP intensity and sensory and musculoskeletal characteristics.
Results: Patients with HSP and patients with SCI-CNP had similar decrease of thermal sensibility in the painful compared to intact body regions and both groups presented similar rates of pathological sensations in painful regions. HSP and SCI-CNP differed however, in the quality of pain and aggravating factors. Significant correlations were found between HSP intensity and heat-pain threshold, presence of subluxation and spasticity.
Conclusions: The similarities between HSP and SCI-CNP and the altered spinothalamic function and sensitization suggest that HSP has neuropathic components in its mechanism. Nevertheless, the unique features of HSP point towards additional possible mechanisms.
Clinical Rehabilitation Impact: The use of specific therapy options for neuropathic pain should be considered when treating patients with HSP.